The invention relates to a pasty electrically resistor composition suitable for preparation of resistive layers, prepared from curable polymer binders having electrically conductive pigments disbursed therein with solvents and, if necessary, with additives. The invention relates further to a resistor layer produced from such resistive composition.
U.S. Pat. No. 3,686,139 describes such a resistive coating paste and resistor elements produced therefrom. To improve service life by resistance to abrasion from wiper contact during use, a selection of heat-curable polymeric material was proposed as a binder for the resistive paste.
Another way to raise the abrasion resistance of resistor layers is suggested in German Application A1-3,638,130. It improves the abrasion properties by admixture of additional agents into the resistive paste.
To reduce the abrasion of resistive layers there is also known the use of pyropolymers as electrically conducting pigment, dispersed into the resistive paste (EP B1 0 112 975, U.S. Pat. No. 4,568,798). This employs hard, fireproof carrier particles, e.g., of aluminum oxide, which are pyrolytically carbonified from the gas phase.
The abrasion resistance of the resistive layer is an essential feature for the service life of an arrangement consisting of a resistive layer. Resistive layers that are not abrasion-resistant lose substance and thereby alter their electrical value. The abraded layer also affects the contact capability of the sliding contact. For some applications, especially in the field of sensors, the abrasion resistance achievable with state-of-the-art methods is not yet adequate.